Mechanism of action of quaternary diamino quenchers in capillary zone electrophoresis

The synthesis of two novel amino compounds, able to quench and reverse the electroosmotic low (EOF) in capillary electrophoresis is here reported. These chemicals are derivatives of two previously described quaternarized piperazines, 1-(4-iodobutyl)-1,4-dimethylpiperazin-1-ium iodide (M1C4I) and 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2.2.2]octane iodide (M7C4I), believed to bind covalently to the silica surface via alkylation of ionized silanols through their terminal, reactive iodine. The novel compounds, although unable to form a covalent bond, due to lack of the o-butyl iodine, are found to be very efficient in suppressing protein interaction with the wall and reversing the EOF. On the basis of their behavior in solution, the minimal structural motifs for strong binding of amino compounds to the silica wall have been derived and are thought to be: (i) the presence of two quaternary nitrogens in the molecule; (ii) a correct distance between said charged nitrogens, represented by a butyl chain (C4); (iii) an hydrophobic “decoration” of the molecules, consisting on a high CH2/N ratio (in the present case 8:1)